Hardness of human tooth, both in enamel and dentin, has been measured at different sites using a Vicker's diamond. In this work we show that these values are almost constant all along the enamel and dentin thicknesses. Indentations were done from outer enamel surface to inner dentin layer, going through the enamel-dentin junction, both in transverse and longitudinal samples. Geometrical well-shape indentation uniformity was checked both with light and with scanning electron microscopes, and the chemical composition of the tooth was analyzed with characteristic X-ray energy dispersive spectroscopy. Hardness measurements were in the range from 270 to 360 VHN for enamel and 50 to 60 VHN for dentin. Cervical zone in longitudinal section showed the lowest value while in transverse sections the highest. All the hardness values were statically significative. Tour results indicate that the difference between enamel and dentin hardness has nothing to do with the content of Na, Cl and Mg, but the percentage of organic and inorganic materials in enamel and dentin.

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Some experimental results have indicated that hydroxyapatite (HA) and octacalcium phosphate (OCP) can form an epitaxic interface. Subsequently the OCP-HA interface has become of great biological interest in the context of mineralized tissue formation. In this work a new OCP-HA interface model based on Brown's proposed configuration [Brown (1962), Nature, 197, 1048-1050] and using the minimum interface free-energy optimization is presented. This new model is formed by half a unit cell of HA and one unit cell of OCP, as in Brown's model, but in our case [1-210] of HA is 'glued' with [010] of OCP. Therefore, the relationship found was: [000-1](HA) parallel to [001](OCP) and [1-210](HA) parallel to [010](OCP). Self-consistent field methods were used for the analysis of Brown's model and ours. It is shown that the atoms in our model have similar environments as in the HA and OCP unit cells and that, as a result of the differences between HA and OCP unit-cell parameters, this interface presents misfit-dislocation-like features. High-resolution transmission electron microscopy (HREM) simulated images for the new interface model have been included and, when they are compared with the experimental ones, the similarity is quite good.

Brushite was synthesized by precipitation of calcium chloride (CaCl(2)) and sodium phosphate monobasic (Na(2)HPO(4)) dried in vacuum and monetite was obtained from this brushite by sonication with a frequency of 90kHz at 500W for 90min. Monetite itself was also transformed in Ca(H(2)PO(4))(2)·H(2)O, monocalcium phosphate monohydrate (MCPM), by sonication with a frequency of 90kHz at 500W for 60min followed by lyophilization. The MCPM was sonicated and lyophilized by three times more until reach over 240min, but any other phase transformation was observed. All these phase transformations were analyzed by X-ray diffraction (XRD) and infrared spectroscopy (FTIR). Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated a grain size of about 200nm in all the samples. The morphology observed was a corn-flake-like grain for brushite, a pseudo-needle-like grains for monetite, and lamellar-like grains for MCPM.

In this work, the influence of three different suspension agents (agar, sodium alginate, and gelatin) in the synthesis of poly(methyl methacrylate) (PMMA) particles is reported. Sodium alginate was the best suspension agent, obtaining characteristics closer to commercial denture base resins. Synthesized particles and two commercial acrylic resins (Acron MC and Lucitone 199) were characterized by light microscopy, scanning electron microscopy, characteristic X-ray energy dispersive spectroscopy, thermogravimetric analysis, and molecular weight measurements. Mechanical tests (transverse deflection behavior) were done using two heat-polymerizing techniques. The results indicated that both the PMMA particles and the commercial acrylic resins have similar characteristics.